This invention relates to oil seal assemblies for use in mechanisms such as engines, pumps, compressors, expanders or the like, and, more specifically, to oil seals for use in such mechanisms wherein the oil seal sealingly engages a working chamber wall when the mechanism is quiescent to provide a static seal.
Prior art of possible relevance includes U.S. Pat. No. 3,905,730, issued Sept. 16, 1975 to Ruf.
Double rail oil seals of the type wherein two rails or strips are capable of relative movement with respect to each other have long been employed in mechanisms such as engines, pumps, compressors, expanders, or the like. In many applications, such as the more typical forms of reciprocating diesel or gasoline engines, they have proved to be quite satisfactoy for their intended purpose. However, in other applications, they will not operate satisfactorily for the reason that they do not provide a static seal, that is, establish a seal between a piston and an operating chamber wall when the mechanism is not being operated. In certain types of reciprocating engines, such as radial engines or inverted V-engines and, to a lesser extent, opposed engines, and in virtually all rotary engines such as trochoidal engines or slant axis rotary engines, such double rail seals are generally unsatisfactory.
Those skilled in the art will immediately recognize that each such mechanism has an operating chamber or combustion chamber at or below the level of the main shaft, with the consequence that lubricating oil can drain under the influence of gravity toward the combustion or operating chamber. Because of the absence of a static seal at the oil ring, the oil may seep into the combustion or operating chamber as the case may be and result in difficulty in starting the engine, decreased combustion efficiency, the introduction of a lubricant into a fluid to be pressurized, etc., not to mention the fact that oil consumption would be undesirably increased.
In the above-identified Ruf patent, there is disclosed the use of double bands or hoops, each of which is slotted with the slot staggered in order to prevent oil from running between the crank case and the operating chambers of a rotary mechanism, as would occur if the slots were not staggered. The use of the slots increases the flexibility of the seals to allow them to more nearly perfectly conform to the surface which they sealingly engage to provide an efficient double rail oil seal. However, in such a construction, oil from a crank case can fill the space occupied by the seal biasing spring and seep into the small gap between the seals which exists because it is physically impossible to make the two hoops mate perfectly unless they are lapped. The oil can then enter the slots and exit the same into the combustion area.
Consequently, such a construction, while theoretically quite efficient, tends to be impractical in the marketplace since it may be utilized in mechanisms of the character of concern only if made with extreme precision which is, of necessity, quite costly.